How can I get special symbols to display properly in the PC Kindle reader app? Specifically, I have card suit symbols (spade, heart, diamond, club) which the calibre ebook reader displays properly and which the iPhone Kindle app displays properly but which the PC Kindle app displays as empty boxes (which are its representation of "unknown character"). These symbols appear in the .xhtml files as:

amp-pound9824; amp-pound9829; amp-pound9830 and amp-pound9827;.

(I used amp-pound here for &# because otherwise the actual symbols displayed.)

I tried changing these to &spades; &hearts; &diams; and &clubs; but that didn't fix the problem. That is, calibre properly converted these to ♠ ♥ ♦ ♣ and that's what I see in calibre's ebook viewer and on my iPhone, but when I copy the MOBI file to the PC's Kindle app, that reader displays the same empty boxes instead of the symbols. Curiously, when I copied one of those boxes to paste here, it displayed as ♥. But that doesn't help. I need the symbols to display properly in the PC app.)

I tried inserting the characters themselves (♠ ♥ ♦ ♣) into the XML files, but those produced unrecognizable characters in both the iPhone Kindle app and the PC Kindle app

I tried converting to AZW3 and EPUB, but the PC Kindle app doesn't recognize those formats.

I tried changing Preferences>Common options>Input character coding to each of the options (cp1252, cp1250, cp1252, cp1253, utf8, etc.), but those options produced either unrecognizable characters or question marks.